In many base station antennas, it is often necessary to incorporate several types of radio frequency (RF) transmission lines in the signal path, from the antenna input connector to the antenna radiating elements. For example, the electrical signal path in a base station antenna can include coaxial cable, printed circuit board microstrips, and air dielectric microstrips, in various combinations.
When different types of transmission lines interface with one another, the signal moves from a first transmission line to a second transmission line. At these junctions, it is critical to maintain transmission line impedance and to avoid and/or minimize introducing passive intermodulation (PIM).
Furthermore, many known electrical RF connections include solder to couple metal-to-metal compression interfaces. Solder mandates that components be made from materials that can accept solder, and typically these materials include a tin-plated brass or a tin-plated copper. Both brass and copper are relatively dense materials and have a relatively high cost as compared to aluminum, which is a relatively light and low cost material. However, aluminum does not accept a solder application.
In view of the above, there is a continuing, ongoing need for an improved transmission line transition.